Anglerfish ovary by James Hayden from the The Wistar Institute
 

This section of flower stem was photographed by Gerd Guenther.
 

This image of olivine within the igneous rock gabbro was taken by Bernardo Cesare.
 

Arlene Wechezak from Anacortes, Washington, took this image of algae and diatoms.
 

Veterinary optometrist Havi Sarfaty took this image of discus fish scales.
 
From New Scientist:

Crossing a microscope with a camera gives you a micrograph, a tiny photograph that allows artists and scientists to show the beauty inaccessible to the naked eye. Every year the Small World competition run by optics giant Nikon celebrates this hidden world. This year the winners range from an anglerfish ovary to the sex organs of plants via a rusted old coin.

 
New Scientist: The world’s smallest art prize
 
Small World: 2009 Winners